1. Technical Field
The present invention relates to exhaust vent systems, and more particularly to an elbow for a dryer exhaust vent conduit.
2. Description of Related Art
A clothes dryer requires a vent to the exterior, which is typically achieved using an exhaust conduit that is enclosed in a wall cavity and which conveys heated air and lint from the dryer to the exterior of the building in which the dryer is placed. The dryer can include a flexible transition hose which connects the dryer appliance to the exhaust conduit. In a common installation configuration, the exhaust conduit within the wall cavity is vertical, and is angled at the bottom of the vertical section in an elbow so that it protrudes horizontally from the wall surface, with the flexible hose leading from the dryer appliance attached to the horizontal section of the conduit. The exhaust conduit may also be angled at the top of the vertical section in a second elbow to allow for a horizontal venting through a wall outlet, or may remain vertical and vent to the roof of a building.
If air flow from the dryer is restricted, there may be inefficient operation of the dryer, which can waste energy and cause damage to the dryer blower. Of greater concern is the possibility of lint buildup within the exhaust conduit due to non sufficient airflow, which can create a potential fire hazard. Airflow restriction can result due to kinking or crushing of the exhaust conduit or the flexible hose, or can result simply due to friction acting on the air from the surface of the conduit or hose. The friction causes the airflow to slow as the air travels further from the dryer blower. This reduction in air speed allows lint traveling in the airflow to settle, creating a dangerous buildup over time.
The typical exhaust conduit elbow can be used within a wall cavity, attic space or crawl space to provide for angles of turn between 0° and 90°. The typical elbow has a 3.25″ radius and is formed of a metal pipe, usually aluminum, which is divided into sections. For example, the elbow may have four sections, each of which may have straight walls, with the two central sections being generally wedge-shaped so that the elbow extends through an angle of turn of approximately 90°. The sections may be connected by crimped or folded metal areas so that the elbow may be flexed slightly to suit the application. The 3.25″ radius is very tight and causes airflow restriction and friction loss, which in turn creates more turbulence and restricts efficient airflow much more than straight sections of the exhaust conduit. The airflow restriction and friction loss of a typical elbow has been calculated to be equivalent to the friction loss as 5 linear feet of straight pipe.
To attempt to alleviate efficiency and lint buildup problems, many building codes place a restriction on the permitted length of dryer exhaust conduits. For a typical exhaust conduit having a diameter of approximately 4″, many building codes restrict the length of the conduit to 25 feet. Additionally, for every 3.25″ elbow introduced in the exhaust conduit to turn the conduit, the permitted length of the conduit is reduced by 5 feet, due to the calculated friction loss in the elbow being equivalent to 5 linear feet of straight pipe. However, space considerations in homes and other buildings often make it difficult to comply with these codes while retaining the greatest amount of usable living space within the building.
It is an object of the present invention to provide an improved elbow for a dryer vent exhaust conduit.